The invention relates to low profile windshield wiper blades and particularly to a pressure distributing superstructure which may be formed of plastic material as for example a reinforced thermoplastic polyester.
Currently windshield wiper blades with plastic superstructures which have been introduced to the market are of the triple yoke design. Such blades are inherently relatively high profile blades. In many modern automobiles the blades are stored in the park position, concealed beneath the cowl. It is desirable to maintain as low a profile as possible so that the blade can pass through the narrow slot provided to reach its concealed park position. Furthermore, a low profile blade is more resistant to windlift and is less distracting during operation. Blade superstructures having their levers pivotally connected and arranged end to end are known from the prior art. Examples of such arrangements are shown in U.S. Patents to Scinta No. 2,616,113 issued Nov. 4, 1952, Hadekel No. 3,386,126 issued June 4, 1968 and Schlegel No. 3,879,793 issued Apr. 29, 1975. In the known prior art separate spring means are provided at each joint to transmit force between the levers. The separate springs increase the weight and complicate assembly techniques. The energy conservation program necessitates every component of a motor vehicle be as light weight as possible.
The Schlegel patent discloses a plastic blade of the type utilizing alternatively either a rubber torsion spring of cylindrical configuration or a coiled torsion spring at each joint. Hadekel discloses a superstructure which utilizes either a coil torsion spring at each joint or alternatively a compression spring straddling the joint. The Scinta patent discloses a flat leaf spring straddling each joint with a housing to enclose the spring and a connecting element to space the pivotal connections. In each of the assemblies described above a separate rivet or pin extends through the joint to form a pivotal axis and retains the levers in assembled relationship. The known constructions require complicated assembly techniques, additional parts not required in stacked lever blades and additional weight. The springs used in prior art construction require that the blade silhouette be extended to accomodate the diameter of the spring or, in the case of the Scinta patent, to accomodate the relatively high bow needed for obtaining the requisite spring force.